A ground source heat pump system comprises at least two subsystems, a heat pump which is installed in a building to be heated, and a ground coil which is buried in the ground adjacent to the building. A ground source heat pump system may also include a third subsystem to transfer heat from the environment to supplement the heat available from the ground.
Ground coils currently used are of various types, which are installed in different ways according to type, the typical installation procedures being as follows.
In the case of a vertical ground coil, bore holes are drilled into the ground and a two-pipe arrangement complete with a lower end turn-around is installed in the bore holes. The pipes are joined at a header, filled with a suitable heat transfer fluid, and then connected to a heat pump. With another vertical ground coil type, a hole is drilled in the ground and a spiral coil is installed in the hole, the hole then being backfilled. Several spiral coils may be involved, and will then be connected to the heat pump.
With a horizontal type of ground coil, a trench is opened and one or more pipes are placed in the trench, and are covered. At the end of the trench adjacent the building the pipes are connected together in the trench with headers which are assembled in the field. After being connected to the heat pump, the ground coil is tested, flushed and filled with heat transfer fluid. In another horizontal type a spiral coil is placed in the trench, the trench then being backfilled. Several spiral coils are usually involved; they are then interconnected by headers, pressure tested, and filled with heat transfer fluid.
With another type, factory assembled coils are placed in a pit, which is then backfilled. The coils are then interconnected by headers.
The installation of currently available ground coils has various disadvantages- It is time consuming, labour intensive and frequently difficult.